2. Field of the Invention
This invention relates to a silver halide photographic emulsion, and particularly relates to a silver halide photographic emulsion having an elevated spectral sensitivity in a green color wavelength region. More specifically the present invention relates to a silver halide photographic emulsion which has a maximum value of spectral sensitivity at a wavelength of 520 nm or more and less than 545 nm, and leads to photographic light sensitive materials having excellent preservability and stability.
2. Description of the Prior Art
As sensitizing dyes having the maximum of spectral sensitivity at a wavelength of 520 nm or more and less than 545 nm, benzimidazolooxazolocarbocyanines (compounds disclosed, for example, in Japanese Patent Publication for Opposition Purpose (hereinafter referred to as "J.P. KOKOKU") No. 44-14030 and the like) and dimethinemerocyanines (compounds disclosed, for example, in U.S. Pat. Nos. 2,493,748, 2,519,001 and 3,480,439) have hitherto been known. As for emulsions containing a benzimidazolooxazolocarbocyanine or a dimethinemerocyanine, increase of fog after application of the emulsions under a high temperature or high temperature and high humidity condition, or lowering of sensitivity owing to poorness of stability with time lapse after application of the emulsions was observed. As sensitizing dyes free from these defects, namely increase of fog under a high temperature or high temperature and high humidity condition, or lowering of sensitivity with time lapse, benzoxazolocarbocyanines (compounds disclosed, for example, in French Patent Nos. 1,108,788, 2,182,329 and 3,514,450, West German Patent No. 2,429,228, and the like) have been known, but the maximum values of spectral sensitivity of benzoxazolocarbocyanines which have hitherto been used are usually in the region of 545 nm or more. Thus it has been very difficult to provide a silver halide photographic emulsion containing a sensitizing dye which has the maximum value of spectral sensitivity at a wavelength of 520 nm or more and less than 545 nm, and is excellent in preservability and stability.